Like the Old Days: Average Fuel Economy Declines in the United States

The longitudinal study conducted at the University of Michigan Transportation Research Institute by Michael Sivak and Brandon Schoettle has been tracking average American fuel economy (window-sticker values) of purchased cars, light trucks, vans, and SUVs since October 2007, according to Douglas McIntyre of 24/7 Wall Street.

According to Sivak, "This large drop likely reflects the increased sales of light trucks and SUVs, and the reduced demand for fuel efficient vehicles of all types because of the falling gas prices." Even though gasoline prices are moving, "toward $4 at times during the most recent three-year period, and hybrids became a larger part of U.S. car sales, some experts believed that car mileage would improve for the foreseeable future."

However, at least for the month of September, American consumers have purchased fewer fuel-efficient vehicles, leading to the greatest drop in fuel economy since December 2011. That being said, September 2014 was the eighth straight month in which average vehicle fuel economy was greater than 25 mpg.